Underpotential deposition detection

Herzog G, Arrigan DWM (2003) Application of disorganized monolayer films on gold electrodes to the prevention of surfactant inhibition of the voltammetric detection of trace metals via anodic stripping of underpotential deposits detection of copper. Anal Chem 75 319-323... 

Blum L, Abruna FI D, White J, Gordon J G, Borges G L, Samant M G and Melroy 1986 Study of underpotentially deposited copper on gold by fluorescence detected surface EXAFS J. Chem. Phys. 85 6732-8... 

For the case of surface truncation rods, the technique is based on the detection of diffraction peaks between Bragg peaks. Although this requires careful alignment and some a priori knowledge of the structure, monolayer sensitivity can be achieved. In fact, Samant et a/.138 have recently performed an in situ surface diffraction study of lead underpotentially deposited on silver employing this technique along with grazing incidence diffraction. It is clear that this technique will also find widespread use in the near future. 

As an example [13] we consider the underpotential deposition of thallium on silver (Fig. 15.13). At potentials above the onset of the upd of thallium the SHG signal decreases, at first slowly, then more rapidly. The adsorption of thallium causes a strong rise in a(o ), because the region in which the electronic density decays to zero becomes more extended with an angle of incidence of 45° this shows up as a drastic increase in the signal. A similar behavior is seen in other systems, and often even fractions of a monolayer can be detected. 

Lead and mercury are deposited as micron-sized clusters, predominantly at intercrystallite boundaries [105] so does lithium from the polyethylene oxide solid electrolyte. What is more, Li intercalates into the sp2-carbon [22, 138], Thus, observations on the Li intercalation and deintercalation enable one to detect non-diamond carbon on the diamond film surface. Copper is difficult to plate on diamond [139], There is indirect evidence that Cu electrodeposition, whose early stages proceed as underpotential deposition, also involves the intercrystallite boundaries [140], We note that diamond electrodes seem to be an appropriate tool for use in the well-known electroanalytical method of detection of traces of metal ions in solutions by their cathodic accumulation followed by anodic stripping. The same holds for anodic deposition, e.g. of, Pb as PbCh with subsequent cathodic reduction [141, 142], Figure 30 shows the voltammograms of anodic dissolution of Cd and Pb cathodically predeposited from their salt mixtures on diamond and glassy carbon electrodes. We see that the dissolution peaks are clearly resolved. The detection limit for Zn, Cd, and Pb is as low as a few ppb [143]. 

Figure 15. Fluorescence-detected (m situ) x-ray absorption spectrum for an underpotentially deposited (UPD) monolayer of copper on a gold (111) electrode with the plane of polarization of the x-ray beam being perpendicular (A) or parallel (B) to the plane of the electrode. Inset Edge region of the x-ray absorption spectrum for a copper UPD monolayer before (C) and after (D) stripping. (From Abruna, H. D., White, J. H., et al., J. Phys. Chem. 92, 7045 (1988), with permission.)...

The most thoroughly characterized surface diffraction study at a single crystal surface is that of underpotentially deposited lead on a silverfl 11) single crystal electrode (epitaxial film on mica). " These investigators began by measuring the CTR of the silver substrate since, unless these were clearly observed, it would be unlikely that diffraction from an electrodeposited monolayer would be detected. 

The spectra show two resonances located around 2065 cm and 1965 cm . The first corresponds to linearly bound CO, the latter was assigned to CO in a bridge-bound position [786]. The conversion of CO in a bridging location into species atop has been identified with SFG [794]. The combination of the high light intensity (e.g. free-electron lasers) and the possibility to obtain absolute spectra without any modulation technique has allowed the detection of generally weak bands like those of over- and underpotential deposited hydrogen on a platinum electrode [795, 796]. Studies of coadsorption of cyanide anions and cetylpyridinium cations on Au(l 11) and Au(210) revealed marked differences [797]. CN is bound... 

The development of the ultrasensitive potential sweep technique, capable of detecting submonolayer amounts of substance on electrode surfaces and its application to metal deposition studies, resulted in detailed investigations of the phenomenon of deposition of metals on foreign substrates at potentials more positive than the thermodynamic reversible potential for the given conditions.This phenomenon has been termed underpotential deposition (UPD). 

In addition to these direct NP oxidation detection experiments, the underpotential deposition (UPD) of metal ions from solution onto metal NPs during collisions between the NPs and an inert electrode was also reported (see Figure 8.18). Reactions for UPD of thallium and bulk electrodeposition of cadmium onto Ag NPs were used for detection, which formed bimetallic core-shell NPs (denoted Ag Tl and Ag Cd, respectively). For the case of thallium, it was shown that up to a... 

Herzog G, Arrigan DWM (2003) Comparison of 2-mercaptoethane sulfonate and mercaptoacetic acid disorganized monolayer-coated electrodes for the detection of copper via underpotential deposition-stripping voltammetry. Electroanalysis 15 1302-1306... 

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